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Se is widely used in many industrial applications. More than 80% of global Se is produced as a by‐product of the copper refining process. It is collected from the anode residue (Hoffmann 1989). The production of Se through refinery processes has increased to 2800 tons (in the year 2018) due to its huge demand in industrial applications (USGS 2020). Refinery production by country is depicted in Figure 3.1. Ammonium selenite is used in glass manufacturing processes to neutralize coloration that has occurred due to iron oxide. Sodium selenate is also used as the soil additive in Se‐deficient areas. Ruby red glass, a variety of glass utilized in tableware, traffic, and other signal lenses and infrared equipment, was manufactured using 1–50 pounds of Se per ton of glass (Weyl 1981). Se in its high purity forms is also employed in semiconductors, specialty transformers, thermo elements, etc. About 23% of the total Se demand is for duplicating machine use. The Se‐coated metal cylinders are employed in the dry photographic copying process in which electricity transfers the photographic image (Joannopoulos 1979). For the each 100 sq. feet of copying surface around 4 pounds of Se is needed (Bureau of Mines 1970). The inorganic pigments which are used in plastics, paints, enamels, inks, rubbers, and ceramics are manufactured using cadmium sulfoselenide (Waitkins et al. 1942).

Figure 3.1 Global refinery production for 2018 and 2019 (USGS 2020).

To increase the resilience of rubber and to promote heat, oxidation, and abrasion resistance, Se compounds are used as accelerators and vulcanizing agents in rubber manufacturing (Dudley 1938). Se is added to the stainless steel during manufacturing, which will improve its characteristic properties such as forging, casting, and machining without sacrificing corrosion resistance. Se compounds such Se dioxides catalyze many organic reactions such as hydrogenation, oxidation, isomerization, and polymerization. Se is extensively utilized to help control micro cracking in electroplated chromium as reducing or oxidizing agent (Rashkov et al. 1983). Due to the antioxidant and antigalling properties of Se it is utilized in insecticides, parasiticides, bactericides and herbicides, mercury vapor detectors, insect repellents, etc. (Mechora 2019). Since 1974 the Food and Drug Administration has removed the ban on Se and established it as an essential micronutrient. Therefore, Se in small amounts is used as a food additive for livestock. Utilization of Se in industrial applications has been proven for a long time and the wastes generated from these industrial applications are polluting the environment day by day.

Se is also used as catalyst in some chemical reactions. In X‐ray crystallography, incorporation of one or more Se atoms in place of sulfur helps with multiple or single wavelength anomalous dispersion. Se is widely used for toning of photographic prints and it intensifies tonal range of black and white photographic images, resulting in improved permanence of prints (Wall 1924). The worldwide consumption of Se in different applications is presented in Figure 3.2.

Figure 3.2 Global consumption of Se (USGS 2020).